Wera 8790 HMB HF Zyklop 3/8in. Drive Sockets - Metric - Wera 05003751001, This 3/8 inch drive Zyklop 17mm socket from Wera has a holding function that retains hexagonal headed bolts or screws in the socket for extremely convenient driving, with reduced risk of losing the bolt or screw when addressing the workpiece.The clamping of the screw is achieved by a twin spring-loaded ball system and is especially helpful in confined, hard-to-reach spaces, where there is no room for a second hand to hold the bolt in the socket. Wera 05003751001 8790 HMB HF Zyklop Socket 3/8\" Drive 17 x 29mm